Bit assembly for bottom hole impact drilling tool



United States Patent [72] Inventor Gerald L. Adcock 2,097,030 10/1937 Killgore... 175/413 511 Airway Drive, Lewiston, Idaho 83501 2,701,126 2/1955 McClennan 175/413 [21] Appl. No. 814,412 1 3,075,593 1/1963 Holsing 175/413 [22] Filed April 8, 1969 3,143,177 8/1964 Galorneau et al. 175/413 [45] Patented Nov. 3,1970 3,152,654 10/1964 Conover 175/413 1 Primary Examiner-James A. Leppink 541 an ASSEMBLY r01: norrom HOLE IMPACT and DRILLING TOOL I 9 Claims 4 Drawing Figs. ABSTRACT: A two piece bit assembly is provided for a bot- [52] U.S. Cl. 175/413 mm hole impact drilling tooL The bit assembly has an any E219 13/00 and a bit threadably mounted on the anvil with a plurality of Search button assemblies mounted in the face of the The button f Ci d assemblies have'tapered sleeves that are forced fit in tapered [56] Re erences bores. Access apertures are provided in the back of the bit to UNITED STATES PATENTS enable the button assemblies to be punched out to replace 1,388,490 8/1921 Suman 175/413 worn buttons.

Patented Novha, 1970 3,537,539

I N VENTOR.

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BIT ASSEMBLY FOR BOTTOM HOLE IMPACT DRILLING TOOL BACKGROUND OF THE INVENTION This invention relates to bottom hole impact boring tool for drilling water wells and the like in the earths crust, and more particularly to hit assemblies for such tools.

Impact bit assemblies are quite expensive and represent a substantial cost in the drilling operation. Wear of the bit assemblies constitutes a serious problem requiring frequent replacement during the drilling of a single well. Often hard metal elements of tungsten carbide are secured to the face of the bit assembly to provide wear resistant cutting elements. When the elements become excessively worn, generally the entire bit assembly must be replaced. Such replacement is extremely expensive.

One of the principal objects of this invention is to provide an improved impact bit assembly for bottom hole impact drilling tools that permits easy removal of worn cutting elements without having to replace the entire bit assembly.

A further object of this invention is to provide an improved two piece impact bit assembly with replaceable cutting elements.

An additional object of this invention is to provide an improved impact bit assembly with novel removable mounting means for attaching the cutting elements to the bit assembly.

A further object of this invention is to provide an improved impact bit assembly to drastically reduce the cost of the drilling operation without jeopardizing the results.

These and other objects and advantages of this invention will become apparent upon a reading of the following detailed description of the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of this invention is illustrated in the accompanying drawings, in which:

FIG. 1 is a partial cross-sectional view of an impact drilling tool showing a bit assembly mounted to the lower end thereof for drilling and cutting the earths crust;

FIG. 2 is an exploded perspective view of the bit assembly showing an anvil member, a bit and an enlarged view of a button assembly;

FIG. 3 is a vertical cross-sectional view taken along line 3-3 in FIG. 2 showing the mounting of a button assembly in the face of the bit; and

FIG. 4 is a cross-sectional view similar to FIG. 3 except showing the removal of a button assembly from the bit.

DETAILED DESCRIPTION or A PREFERRED EMBODIMENT Referring to FIG. 1 there is shown a common bottom hole impact drilling tool that is operated by compressed air. The tool 10 is generally operated by a 100 p.s.i. or 200 p.s.i. compressed air system. A bit assembly 11 embodying this invention is attached to the lower end of the drilling tool having a plurality of cutting button assemblies 12, individually identified 12a-p projecting therefrom.

To adequately understand the features of the bit assembly it is useful to be acquainted with the structure and operation of a bottom hole percussion or impact drilling tool.

The impact drilling tool shown in FIG. 1 has a cylindrical top assembly 14 with an intake 15 for attaching to the lower end of the drill pipe. An internal shoulder 16 is formed in the top assembly forming a valve seat 17.

A cylindrical control subassembly 18 is mounted to the bottom of the top assembly contained control mechanisms. The control assembly 18 has a tubular housing 20 with a cylindrical control rod 21 mounted therein and extending downward therefrom. The control rod has a bore 22 formed coaxially therethrough. A counterbore 23 is formed in the bore 22 for supporting a check valve 24 having a spring 25 biasing the check valve upwardly'to seat the valve against the surface 17 when the air pressure from the source decreases below a prescribed level to prevent reverse flow of the air.

Ports 28 are formed in the control rod at the upper end of the control rod 21 communicating with the intake and the bore 22. An annular shoulder 30 is formed on the outer surface of the control rod 21 adjacent the upper end thereof with resilient rings 31 and 32 mounted above and below the shoulder respectively for maintaining and holding the control rod in place while permitting slight vertical movement against either of the rings 31 and 32.

A main body housing 33 is mounted to the lower end of the control assembly 18 surrounding the control rod 21. The housing 33 has a freely movable piston 34 mounted therein surrounding the control rod 21 for movement therealong. An upper chamber 35 is formed radially between the tubular piston housing 33 and control rod immediately above the piston 34 and a lower chamber 36 is formed between the tubular piston housing 33 and the control rod immediately below the piston 34.

The piston 34 has a bore 40 therethrough for slidably receiving the control rod. An inner annular groove 41 is centrally formed in the bore 40. A high pressure port 42 extends from the rod bore 22 tothe outer surface thereof for communicating with the annular groove 41 of the piston. An upper groove 43 is formed in the side of the control rod 21 for communicating high pressure between the upper chamber 35 and annular groove 41 when the piston is in the up position.

A lower groove 44 is formed in the side of the control rod 21 for communicating high pressure between the lower chamber 36 and the inner annular groove 41 when the piston is in the down position.

A choke 46 is mounted in the bore 22 adjacent to the lower end of the control rod for limiting the pressure drop within the bore while permitting the escape of compressed fluid air at a lower pressure from the bottom of the control rod.

An upper relief port 50 is formed in the side of the control rod for exhausting the air from the upper chamber 35. A lower relief port 51 is formed in the control rod adjacent the lower chamber 36 for exhausting pressure therefrom when the piston moved to the lower position. A passageway 52 interconnects the upper relief port 50 and the lower relief port 51 and extends downward to the end of the control rod for exhausting the pressure from the tool.

The bit assembly 11 includes a cylindrical anvil 54 that is slidably mounted in the lower end of the tubular piston housing 33. The anvil 54 has a bore 55 extending therethrough. The anvil has an upper end 55 forming part of the lower chamber 36 to receive the lower end of the piston 34 thereagainst to transmit impact force therethrough. A counterbore 56 is formed in the upper end of the bore 55 for slidably receiving the lower end of the control rod 21. The upper end of the anvil 54 has seals mounted on the circumference thereof for slidable engagement with the tubular piston housing 33 to prevent the loss of pressure therebetween.

The anvil 54 has a reduced outer center section 57 with angularly spaced longitudinal splines 60 formed thereon for preventing the rotation of the anvil with respect to the tool and for assisting in the mounting of the bit assembly 11 to the tool 10.

The anvil 54 has an enlarged lower end 61 with an extending reduced end section 62 that has threads formed thereon. The reduced section 62 forms an annular bearing shoulder 64. A spline mounting skirt 65 is mounted over the anvil 54 and is threadably mounted to the lower end of the tubular piston housing 33 for slidably securing the bit assembly to the tool.

The bit assembly 11 also includes a cylindrical bit 70 which is removably mounted to the anvil 54. The cylindrical bit 70 has a cylindrical side surface 71, a back surface 72 and a face surface 73. A cylindrical cavity or bore 75 is formed in the back surface 72 coaxially with the center line of the tool for receiving the lower end of the anvil 54. The cavity 75 has cylindrical side wall 77 and a flat base 78. Threads 80 are formed in the side wall 77 for threadably receiving the reduced end section 62 of the anvil 54 therein. The back sur face 72 includes an annular flat surface 81 that seats against the annular bearing shoulder 64 of the anvil when the hit 70 is mounted to the anvil.

Air holes 82a and 82b extend from the central cavity 75 to the face surface 73 for permitting the escape of compressed air from the tool to assist in the removal of the earth material cut from the bottom of the hole being drilled.

The cylindrical side surface 71 has a bevelled side surface 33 communicating with the back surface 75. Longitudinal grooves 84 are formed in the side surface 81 in a symmetrical configuration to facilitate the flow of compressed air and earth material from the hole past the bit and upwardly along the side of the drilling tool 10.

The face surface 73 includes an annular flat front surface 85 and an inclined annular surface 86 communicating with the side surface 71.

A plurality of tapered bores or apertures 88 corresponding to the button assemblies 12 are formed in the face surface 73 at various acute angles A to the center line of the drilling tool for receiving the button assemblies 12 therein. lt has been found that for best results the button assemblies are mounted at different angles depending upon their location on the face surface 73.

in one particular embodiment the tapered bores 88 for the button assemblies 12a-d have center lines that intersect the center line ofthe tool at approximately 50. The tapered bores 88 for the button assemblies 120-!1 are formed at an acute angle of 45 to the center line of the tool. The bores 88 receiving the button assemblies i and j are formed at 25 to the center line of the tool. The bores for button assemblies k and l are aligned at to the center line of the tool. The bores for the button assemblies m and n are aligned at 9 to the center line of the tool. The bores for the button assemblies 0 and p are formed parallel with the center line of the tool or at an acute angle of 0.

Each of the tapered bores 88 has a tapered side wall 90 that extends inward from the face surface 73. The side wall 90 terminates at the bore bottom 91.

Access apertures 92 are formed in the bit 70 extending from the back surface 72 to the tapered bores 38 along the center axes of the bores to provide access to the bores 88. After the button assemblies become excessively worn, the bit is removed from the anvil and the button assemblies are punched out as shown in FIG. 4.

Each of the button assemblies 12 includes a taper sleeve 95 (HO. 2) having a large end 96 and a small end 97 with a tapered outer wall 98 having a taper corresponding to the taper of the bores 88. The large end 96 has a bevelled front surface. A bore 100 is formed coaxially in the large end 96 producing a side wall 101 and a bottom 102. A slit 103 is formed in the tapered sleeve extending from the wall 98 to the center line of the sleeve to permit circumferential contraction and expansion of the sleeve.

A cylindrically-shaped button 104 of a hard metal material such as tungsten carbide is mounted in the bore 100 with the front end 106 extending outward from the sleeve for engaging the earth. The front end 106 is rounded as shown in the drawings. The sleeve 95 is made of a softer material than the button.

During the mounting of the button assemblies 12 to the bit 70 the buttons 104 are initially slidably mounted in the bores 100. The tapered sleeves are then forced-fit into the tapered bores 88 until the small ends 97 abut the bottoms 91 of the bores. During the mounting process the sleeve contracts to securely grip and hold the button within the bore 100 to prevent the button from becoming loose and being dislodged during the drilling operation.

It is found that a bore and sleeve taper of six-tenths inch per foot is quite adequate to produce a forced-fit without causing the button assemblies to pop out under stress. The slit 103 is provided to accommodate a forced-fit without damaging the side wall of the bore or the outer surface wall 97 of the sleeve.

The bit 70 is then threadably mounted on the lower end of the anvil 54. The anvil and the bit are mounted in the lower end of the impact drilling tool with the upper end of the anvil extending upwardly into the housing 33 to receive the pounding or impact action of the lower end of the piston 34. During the operation of the impact drilling tool high compressed air is forced downwardly through the center of the control rod 21 and out the high pressure port 42 to communicate with the annular groove 41 of the piston. P16. 1 shows the annular groove 41 extending between the high pressure port 52 and the lower side groove 44 to apply high pressure to the lower chamber 34. This causes the piston to move upward with the air in the upper chamber 35 exhausting out through the relief port 50. As the piston moves upwardly the annular groove 41 discon' tinues communicating with the lower groove 44 and begins to communicate with the upper groove 43 to apply the high pressure to the upper chamber 34.

The relief port 40 is positioned along the control groove so that not all of the air exhausted out of the port 40. A sufficient amount of air is retained in the upper chamber to provide a cushion to prevent the upper end of the piston from engaging the control assembly 18. However, this is not the case on the return down stroke. The piston is accelerated downwardly to impact the lower end of the piston against the upper end of the anvil to generate an impact force through the bit assembly to buttons 104.

ln addition to the impact force generated, frequently the tool 10 is rotated slowly between 10 and 30 r.p.m. to continually shift the position of the buttons to cover the entire bottom of the hole.

After the buttons become excessively worn the percussion tool 10 is removed from the hole and the bit 70 is threadably removed from the anvil 54. A punching means is then used to extend into the access apertures 92 to engage the tapered sleeves and punch the sleeves 95 outwardly to permit the easy removal of the buttons. New buttons are then inserted into the sleeves.

The. preferred embodiment just described enables the operator to quickly and efficiently provide new cutting ele' ments without removing and discarding the entire bit assembly. This greatly reduces the cost of operation and enables the operator to change the cutting elements in a short period of time to reduce the down time of the drilling rig. It has been estimated that the maintenance cost of the bit assembly can be decreased almost five fold over previously used apparatus.

lclaim:

l. A bit assembly for a bottom hole impact drilling tool comprising:

a cylindrical anvil with an upper end for fitting within the impact drilling tool and a lower end for extending downward from the impact drilling tool coaxially with a center line;

a cylindrically-shaped bit removably mounted to the lower end of the anvil coaxially with the center line, said bit having a back surface and a face surface;

said bit having a plurality of radially extending tapered bores formed in the face surface at acute angles to the center line;

tapered button assemblies forced-fit in the bores with cutting buttons extending outward from the face surface for engaging the bottom of the hole; and

said bit having a plurality of access apertures formed in the back surface, aligned and communicating with the tapered bores for enabling the tapered button assemblies to be pushed from the bores when the bit is removed from the anvil to replace buttons when they become excessively worn.

2. A bit assembly as defined in claim 1 wherein the lower end of the anvil is threaded and wherein a threaded cylindrical cavity is formed in the back surface ofthe bit for receiving the lower end of the anvil to form a removably rigid mounting between the anvil and the bit.

3. A bit assembly as defined in claim 1 wherein the arcuate angles of the tapered bores are between 0 and 50.

4. A bit assembly as defined in claim 1 wherein the face surface includes an annular bevelled surface communicating with a cylindrical side surface of the bit.

5. A bit assembly as defined in claim 4 wherein side grooves are symmetrically formed in the side surface to facilitate the flow of earth material from the bottom of the hole.

6. A bit assembly as defined in claim 1 wherein each of the tapered button assemblies has:

a relatively soft tapered metal sleeve with a bore formed therein at the larger end thereof;

a hard metallic button mounted in the sleeve bore and extending outward from the larger end; and

said sleeve having a side slit formed therein communicating with the bore to cause the sleeve to contract to securely grip the button when the sleeve is forced in a bit bore.

7. In a bit assembly for a bottom hole impact drilling tool:

a bit having a front surface with a plurality of tapered apertures formed therein;

button assemblies mounted in the tapered apertures;

each of said button assemblies having a tapered sleeve with a bore formed in one end thereof and a radial side slit formed therein running the length of the sleeve; and

a button mounted in the bore and adapted to be held securely in the bore when the button assembly is forcedfit into the bore to contract the sleeve and the bore gripping the button.

8. In a bit assembly as definedin claim 7 wherein the taper of the apertures and sleeves is approximately 0.6 inches per foot ' l 9. In a bit assembly as defined in claim 7 wherein the apertures are formed at acute angles to a center line of the bit. 

